Re-land "Check in a simple pure-python based Markdown previewer."

third_party/Python-Markdown/markdown/serializers.py

+# markdown/searializers.py
+#
+# Add x/html serialization to Elementree
+# Taken from ElementTree 1.3 preview with slight modifications
+#
+# Copyright (c) 1999-2007 by Fredrik Lundh.  All rights reserved.
+#
+# fredrik@pythonware.com
+# http://www.pythonware.com
+#
+# --------------------------------------------------------------------
+# The ElementTree toolkit is
+#
+# Copyright (c) 1999-2007 by Fredrik Lundh
+#
+# By obtaining, using, and/or copying this software and/or its
+# associated documentation, you agree that you have read, understood,
+# and will comply with the following terms and conditions:
+#
+# Permission to use, copy, modify, and distribute this software and
+# its associated documentation for any purpose and without fee is
+# hereby granted, provided that the above copyright notice appears in
+# all copies, and that both that copyright notice and this permission
+# notice appear in supporting documentation, and that the name of
+# Secret Labs AB or the author not be used in advertising or publicity
+# pertaining to distribution of the software without specific, written
+# prior permission.
+#
+# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
+# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
+# ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
+# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+# --------------------------------------------------------------------
+
+
+from __future__ import absolute_import
+from __future__ import unicode_literals
+from . import util
+ElementTree = util.etree.ElementTree
+QName = util.etree.QName
+if hasattr(util.etree, 'test_comment'):  # pragma: no cover
+    Comment = util.etree.test_comment
+else:  # pragma: no cover
+    Comment = util.etree.Comment
+PI = util.etree.PI
+ProcessingInstruction = util.etree.ProcessingInstruction
+
+__all__ = ['to_html_string', 'to_xhtml_string']
+
+HTML_EMPTY = ("area", "base", "basefont", "br", "col", "frame", "hr",
+              "img", "input", "isindex", "link", "meta" "param")
+
+try:
+    HTML_EMPTY = set(HTML_EMPTY)
+except NameError:  # pragma: no cover
+    pass
+
+_namespace_map = {
+    # "well-known" namespace prefixes
+    "http://www.w3.org/XML/1998/namespace": "xml",
+    "http://www.w3.org/1999/xhtml": "html",
+    "http://www.w3.org/1999/02/22-rdf-syntax-ns#": "rdf",
+    "http://schemas.xmlsoap.org/wsdl/": "wsdl",
+    # xml schema
+    "http://www.w3.org/2001/XMLSchema": "xs",
+    "http://www.w3.org/2001/XMLSchema-instance": "xsi",
+    # dublic core
+    "http://purl.org/dc/elements/1.1/": "dc",
+}
+
+
+def _raise_serialization_error(text):  # pragma: no cover
+    raise TypeError(
+        "cannot serialize %r (type %s)" % (text, type(text).__name__)
+        )
+
+
+def _encode(text, encoding):
+    try:
+        return text.encode(encoding, "xmlcharrefreplace")
+    except (TypeError, AttributeError):  # pragma: no cover
+        _raise_serialization_error(text)
+
+
+def _escape_cdata(text):
+    # escape character data
+    try:
+        # it's worth avoiding do-nothing calls for strings that are
+        # shorter than 500 character, or so.  assume that's, by far,
+        # the most common case in most applications.
+        if "&" in text:
+            text = text.replace("&", "&")
+        if "<" in text:
+            text = text.replace("<", "&lt;")
+        if ">" in text:
+            text = text.replace(">", "&gt;")
+        return text
+    except (TypeError, AttributeError):  # pragma: no cover
+        _raise_serialization_error(text)
+
+
+def _escape_attrib(text):
+    # escape attribute value
+    try:
+        if "&" in text:
+            text = text.replace("&", "&amp;")
+        if "<" in text:
+            text = text.replace("<", "&lt;")
+        if ">" in text:
+            text = text.replace(">", "&gt;")
+        if "\"" in text:
+            text = text.replace("\"", "&quot;")
+        if "\n" in text:
+            text = text.replace("\n", "&#10;")
+        return text
+    except (TypeError, AttributeError):  # pragma: no cover
+        _raise_serialization_error(text)
+
+
+def _escape_attrib_html(text):
+    # escape attribute value
+    try:
+        if "&" in text:
+            text = text.replace("&", "&amp;")
+        if "<" in text:
+            text = text.replace("<", "&lt;")
+        if ">" in text:
+            text = text.replace(">", "&gt;")
+        if "\"" in text:
+            text = text.replace("\"", "&quot;")
+        return text
+    except (TypeError, AttributeError):  # pragma: no cover
+        _raise_serialization_error(text)
+
+
+def _serialize_html(write, elem, qnames, namespaces, format):
+    tag = elem.tag
+    text = elem.text
+    if tag is Comment:
+        write("<!--%s-->" % _escape_cdata(text))
+    elif tag is ProcessingInstruction:
+        write("<?%s?>" % _escape_cdata(text))
+    else:
+        tag = qnames[tag]
+        if tag is None:
+            if text:
+                write(_escape_cdata(text))
+            for e in elem:
+                _serialize_html(write, e, qnames, None, format)
+        else:
+            write("<" + tag)
+            items = elem.items()
+            if items or namespaces:
+                items = sorted(items)  # lexical order
+                for k, v in items:
+                    if isinstance(k, QName):
+                        k = k.text
+                    if isinstance(v, QName):
+                        v = qnames[v.text]
+                    else:
+                        v = _escape_attrib_html(v)
+                    if qnames[k] == v and format == 'html':
+                        # handle boolean attributes
+                        write(" %s" % v)
+                    else:
+                        write(" %s=\"%s\"" % (qnames[k], v))
+                if namespaces:
+                    items = namespaces.items()
+                    items.sort(key=lambda x: x[1])  # sort on prefix
+                    for v, k in items:
+                        if k:
+                            k = ":" + k
+                        write(" xmlns%s=\"%s\"" % (k, _escape_attrib(v)))
+            if format == "xhtml" and tag.lower() in HTML_EMPTY:
+                write(" />")
+            else:
+                write(">")
+                if text:
+                    if tag.lower() in ["script", "style"]:
+                        write(text)
+                    else:
+                        write(_escape_cdata(text))
+                for e in elem:
+                    _serialize_html(write, e, qnames, None, format)
+                if tag.lower() not in HTML_EMPTY:
+                    write("</" + tag + ">")
+    if elem.tail:
+        write(_escape_cdata(elem.tail))
+
+
+def _write_html(root,
+                encoding=None,
+                default_namespace=None,
+                format="html"):
+    assert root is not None
+    data = []
+    write = data.append
+    qnames, namespaces = _namespaces(root, default_namespace)
+    _serialize_html(write, root, qnames, namespaces, format)
+    if encoding is None:
+        return "".join(data)
+    else:
+        return _encode("".join(data))
+
+
+# --------------------------------------------------------------------
+# serialization support
+
+def _namespaces(elem, default_namespace=None):
+    # identify namespaces used in this tree
+
+    # maps qnames to *encoded* prefix:local names
+    qnames = {None: None}
+
+    # maps uri:s to prefixes
+    namespaces = {}
+    if default_namespace:
+        namespaces[default_namespace] = ""
+
+    def add_qname(qname):
+        # calculate serialized qname representation
+        try:
+            if qname[:1] == "{":
+                uri, tag = qname[1:].split("}", 1)
+                prefix = namespaces.get(uri)
+                if prefix is None:
+                    prefix = _namespace_map.get(uri)
+                    if prefix is None:
+                        prefix = "ns%d" % len(namespaces)
+                    if prefix != "xml":
+                        namespaces[uri] = prefix
+                if prefix:
+                    qnames[qname] = "%s:%s" % (prefix, tag)
+                else:
+                    qnames[qname] = tag  # default element
+            else:
+                if default_namespace:
+                    raise ValueError(
+                        "cannot use non-qualified names with "
+                        "default_namespace option"
+                        )
+                qnames[qname] = qname
+        except TypeError:  # pragma: no cover
+            _raise_serialization_error(qname)
+
+    # populate qname and namespaces table
+    try:
+        iterate = elem.iter
+    except AttributeError:
+        iterate = elem.getiterator  # cET compatibility
+    for elem in iterate():
+        tag = elem.tag
+        if isinstance(tag, QName) and tag.text not in qnames:
+            add_qname(tag.text)
+        elif isinstance(tag, util.string_type):
+            if tag not in qnames:
+                add_qname(tag)
+        elif tag is not None and tag is not Comment and tag is not PI:
+            _raise_serialization_error(tag)
+        for key, value in elem.items():
+            if isinstance(key, QName):
+                key = key.text
+            if key not in qnames:
+                add_qname(key)
+            if isinstance(value, QName) and value.text not in qnames:
+                add_qname(value.text)
+        text = elem.text
+        if isinstance(text, QName) and text.text not in qnames:
+            add_qname(text.text)
+    return qnames, namespaces
+
+
+def to_html_string(element):
+    return _write_html(ElementTree(element).getroot(), format="html")
+
+
+def to_xhtml_string(element):
+    return _write_html(ElementTree(element).getroot(), format="xhtml")